AC Booster and BB Preamp are two types of guitar pedals that serve different purposes.
An AC Booster is a type of clean boost pedal that increases the overall volume of the guitar signal without adding any additional gain or distortion.
It can be used to push the front end of an amplifier into overdrive or to help the guitar cut through a mix in a live or recording setting.
A BB Preamp, on the other hand, is a type of preamp pedal that provides a gain boost and often includes tone-shaping capabilities.
It is designed to add more gain and saturation to the guitar signal and can be used to shape the tone of the guitar and drive the amplifier harder.
In short, an AC Booster provides a clean volume boost, while a BB Preamp provides a gain boost and tone shaping.